diff --git a/arn/Inventory.go b/arn/Inventory.go
index f580ed64..47164bb1 100644
--- a/arn/Inventory.go
+++ b/arn/Inventory.go
@@ -62,6 +62,11 @@ func (inventory *Inventory) SwapSlots(a, b int) error {
 	return nil
 }
 
+// GetID returns the ID.
+func (inventory *Inventory) GetID() string {
+	return inventory.UserID
+}
+
 // NewInventory creates a new inventory with the default number of slots.
 func NewInventory(userID UserID) *Inventory {
 	inventory := &Inventory{
diff --git a/arn/InventoryAPI.go b/arn/InventoryAPI.go
index a8c455b5..465a1c72 100644
--- a/arn/InventoryAPI.go
+++ b/arn/InventoryAPI.go
@@ -7,6 +7,11 @@ import (
 	"github.com/aerogo/api"
 )
 
+// Force interface implementations
+var (
+	_ Identifiable = (*Inventory)(nil)
+)
+
 // Actions
 func init() {
 	API.RegisterActions("Inventory", []*api.Action{
diff --git a/arn/NickToUser.go b/arn/NickToUser.go
index d941c79d..8d666fc5 100644
--- a/arn/NickToUser.go
+++ b/arn/NickToUser.go
@@ -5,3 +5,8 @@ type NickToUser struct {
 	Nick   string `json:"nick" primary:"true"`
 	UserID UserID `json:"userId"`
 }
+
+// GetID returns the primary key which is the nickname.
+func (mapping *NickToUser) GetID() string {
+	return mapping.Nick
+}
diff --git a/arn/ShopItemAPI.go b/arn/ShopItemAPI.go
index 8a770fdf..0a6b216c 100644
--- a/arn/ShopItemAPI.go
+++ b/arn/ShopItemAPI.go
@@ -1,5 +1,10 @@
 package arn
 
+// Force interface implementations
+var (
+	_ Identifiable = (*ShopItem)(nil)
+)
+
 // Save saves the item in the database.
 func (item *ShopItem) Save() {
 	DB.Set("ShopItem", item.ID, item)